You'd be right to doubt whether or not Jupiter
actually orbits the sun, or if you could survive the planet's
sickening radiation belt, but make no mistake about its size.
At more than 89,000 miles in diameter and about 318 times more
massive than Earth — within the ballpark of being
a failed star — Jupiter is absolutely humongous.
NASA's 4-ton, basketball court-size
Juno spacecraft reached the gas giant on July 4, 2016.
But that's long after the Cassini space probe briefly visited
Jupiter in 2001, on its way to Saturn.
To understand just how big the former world really is, gaze at
this
Cassini photo of Jupiter's hellish, sulfur-spewing moon Io
cast against the planet's clouds:
Io is roughly the size of Earth's moon and orbits above Jupiter
at roughly the same distance, as NASA explains at its July 7, 2016, Astronomy
Picture of the Day.
Still not grasping that?
Here's Io, the yellow-covered moon that's pockmarked with
hundreds of volcanoes, set next to Earth and its moon:
Gregory
H. Revera/NASA/JPL/University of Arizona
Jupiter's size makes it a terribly difficult place to explore,
since its strong gravity corrals and accelerates the belches
of Io's volcanoes into high-speed particles and radiation.
This is also why Juno's mission should prove revolutionary: Few
spacecraft have gotten or will ever get as close to Jupiter.
An illustration of the
Juno spacecraft around Jupiter.
NASA
During its
jam-packed year-long mission, the probe will dive
through the planet's clouds, "taste" the radiation belts,
take photos, record
beautiful polar auroras, and round up clues that might reveal
what Jupiter's core is made of — and if it's solid at its core.
But the science Juno can pull off will be limited.
The reason is because the
probe lacks a radioisotope power source, or nuclear
battery, like the ones on Cassini, Galileo, Voyager, and
other spacecraft that came before this latest Jovian mission.
Instead of generating electricity using red-hot
plutonium-238, which is extremely
limited in supply (despite production kicking off
for the first time since the end of the Cold War), Juno
relies on three sensitive, bus-size solar panels. To avoid
destroying them with radiation, Juno has to perform some
extreme acrobatics during its visit.
After Juno finishes exploring the gargantuan planet, its fate
will not be pretty.
To protect any aliens that might be living on icy moons such as
Europa and Ganymede, NASA intends to
fly the $1 billion probe to its doom — right into the
seemingly bottomless, noxious clouds of Jupiter.
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